1. Field
The following description relates to a mobile communication system, and more particularly, to a wireless channel sounder that analyzes the characteristics of the wireless channels, and that performs spatial channel modeling based on the results of the analysis.
2. Description of the Related Art
Mobile communication technologies are being evolved to combine transmission diversity and multi-user diversity and to provide cooperative communications to increase the transmission capacity of mobile communication systems. Cooperative mobile communication is a technique for the design and embodiment of next-generation mobile communication networks in which multiple links exist in a complex manner, and have attracted public attention as a suitable mobile communication technique to improve wireless transmission capacity using base stations (BSs), mobile stations (MSs), and relay stations (RSs), remove wireless dead zone areas, and expand the cell coverage of mobile communication devices.
Cooperative mobile communication involves using a wireless communication system that is equipped with multiple input multiple output (MIMO) antennas, and whose performance varies depending on the spatial characteristics of MIMO channels that vary constantly over time. That is, a wireless communication system equipped with MIMO antennas may be more sensitive than a wireless communication system equipped with single input single output (SISO) antennas to the characteristics of wireless channels. Thus, it is important to precisely determine the characteristics of wireless channels for the design of a wireless communication system with MIMO antennas.
Next-generation wireless communication systems using MIMO antennas may be used in urban areas, and particularly, in an indoor environment for high-speed wireless data transmission. To develop a next-generation mobile communication system such as, for example, an IMT-Advanced system, the analysis and mathematical modeling of the propagation characteristics of spatial channels including MIMO channels in wireless interface area may be required. Since the characteristics of wireless channels vary depending on a frequency band, the characteristics of the ground and features on the ground, and the climate, it is necessary to perform wireless channel measurement in various environments and acquire and analyze precise wireless channel measurement data for a reliable wireless channel modeling.
Conventional MIMO antenna wireless channel measurement apparatuses, which are also referred to as channel sounders, are unidirectional measurement systems including a transmitter (TX) system and a receiver (RX) system. To perform wireless channel measurement in urban areas (such as, for example, urban macro or urban micro areas) or areas with complicated traffic patterns, a TX system and TX MIMO antennas may be installed at a BS building or a steel tower that stand higher than neighboring buildings, and an RX system and RX MIMO antennas may be installed at a vehicle that is on the move along a predetermined route. This type of wireless channel measurement is characterized by performing wireless channel measurement and collecting wireless channel measurement data along the path of movement of the vehicle.
However, there is a limit in measuring all the links between BSs, MSs, and RSs in a next-generation mobile communication network where complex multiple links exist by using a conventional channel sounder. For a statistically reliable wireless channel modeling, a considerable number of sample data needs to be collected from a variety of environments. However, conventionally, wireless channel measurement may need to be performed as many times as there are links to be measured, which is extremely inconvenient, time-consuming and costly.
That is, to collect wireless channel measurement data from a complex mobile communication network and model the characteristics of wireless channels, each link in the complex mobile communication network may need to be measured more several times. However, this type of wireless channel measurement may not be suitable for collecting wireless channel measurement data from an environment in which the characteristics of wireless channels continue to vary.